In recent history, technology has allowed the world to become increasingly integrated and globalized. Many companies are now global entities, comprising offices and manufacturing sites geographically dispersed throughout the world. People also are more likely than ever to change their residence multiple times during their lives. With such an integrated, yet geographically diverse world, people often need to communicate with others who are far away. In order to facilitate this communication, teleconferencing and video conferencing are commonplace. Teleconferencing connects two or more parties over a network. The parties often rely upon a conferencing system that may include a microphone and a speaker. Video conferencing further includes a camera and a video monitor allowing the parties to converse while viewing video images of each other.
Teleconferencing and video conferencing systems both commonly suffer from the problem of acoustic echo, which is a delayed and distorted version of an original sound reflected back to its source. Traditionally, a system prone to acoustic echo problems includes a speaker/microphone pair on both ends (called the near-end and the far-end) of the connection. When near-end participants talk, their voices are picked up by the near-end microphone, transmitted to the far-end, and presented as a sound signal via the far-end speaker. The far-end microphone will also pick up this sound signal, directly or indirectly, and the far-end system will send it back to the near-end. This causes the near-end participants to hear a delayed and distorted version of their own speech, which decreases the perceived audio quality.
Acoustic echo reduction (AER) systems are part of practically all speakerphone (e.g., teleconferencing and/or videoconferencing) communication systems. Modern AER systems usually comprise a two phase process to reduce acoustic echo problems. An Acoustic Echo Canceller will perform a first stage of acoustic echo reduction (e.g., Acoustic Echo Cancellation (AEC)) resulting in a signal that has a remaining residual echo (e.g., a portion of the original acoustic echo that could not be reduced). An Acoustic Echo Suppressor will perform a second stage of echo reduction (e.g., Acoustic Echo Suppression (AES)) to reduce the residual echo in the signal output from the Acoustic Echo Canceller, thereby further improving the Echo Return Loss Enhancement (ERLE) of the AER system.
Although the problem of echo reduction has been described in the context of teleconferencing and video conferencing, it will be appreciated that it can also occur whenever a speaker and microphone are configured to be in a closed loop.